The failure of Graduated Pressure was foretold even before it was implemented. In 1964, two eerily prophetic Pentagon war games exposed fatal flaws in the strategy. In those war games, Southeast Asia experts played the role of the North Vietnamese government. In response to limited bombing designed to signal American resolve, those experts decided to infiltrate large numbers of North Vietnamese Army soldiers into the Central Highlands of South Vietnam. This, in turn, impelled the commitment of American troops to the South. The war games concluded that the combination of enemy sanctuaries in North Vietnam, Cambodia and Laos, the enemy’s ability to sustain itself on meager provisions, its strategy of emphasizing political and military actions to avoid strength and attack weakness, and limitations on the application of American military power, would mire the United States in a protracted conflict with little hope for success. The game ended after five years of fighting with five hundred thousand troops committed in South Vietnam. Bundy, however, found the conclusion to be “too harsh.” Rather than force a reexamination of strategy, the results of the SIGMA I and SIGMA II war games appear, in retrospect, as a roadmap that civilian and military leaders followed along the path to failure in Vietnam.McMaster goes on to note that "The SIGMA war games had no effect on American policy or strategy in Vietnam." Why is that? On the surface, the games were extremely well positioned to have a major impact. Certainly, there was a need for sober reexamination of the underlying assumptions of U.S. strategy. Harold Ford cited a CIA officer’s comment on Sigma I-64:
“Widespread at the war games were facile assumptions that attacks against the North would weaken DRV capability to support the war in South Vietnam, and that such attacks would cause the DRV leadership to call off the VC. Both assumptions are highly dubious, given the nature of the VC war.”Gaming with a broad cross-section of participants can serve to identify and challenge the assumptions they bring with them, and in this case there were participants in the Sigma games that did not share the predominant view of the conflict. Sigma I-64 was played by “working level CIA, State, and military officers.” Sigma II-64 also involved high-level policy officials, including National Security Adviser McGeorge Bundy, DCI John McCone, General Curtis LeMay, General Earle Wheeler, and A/S Defense John McNaughton, Deputy Secretary of Defense Cyrus Vance, Deputy CNO Admiral Horacio Rivero, Jr., A/S State William Bundy, and CIA deputy director for intelligence Ray Cline. This is an exceptionally high-level group to find participating in a wargame, but it does not appear that the Sigma wargames of 1964 had any direct impact on policy, despite their dire warnings about the potential consequences of U.S. actions and despite the participation of numerous military and civilian national security leaders. Without a willingness to be persuaded on the part of decision-makers, the games could not make a policy impact. While the results of Sigma I and II were uncannily prescient, the failure of participants to take the results seriously is not the most significant issue; policy-makers are right to be skeptical of a game's predictive value. But by failing to move policy-makers to reexamine their assumptions from a fresh perspective, the Sigma games represent a colossal missed opportunity.
(Thomas Allen's 1987 book, War Games, has a chapter on the Sigma games (pp. 193-208). See also Harold Ford, CIA and the Vietnam Policymakers: Three Episodes 1962-1968, pages 57, 58, and 67.)